Iberian gauge (Spanish: ancho ibérico, trocha ibérica, Portuguese: bitola ibérica) is a track gauge of 1,668 mm (5 ft 5+21⁄32 in), most extensively used by the railways of Spain and Portugal.
The main railway networks of Spain were initially constructed to a 1,672 mm (5 ft 5+13⁄16 in) gauge of six Castilian feet.
[2] Since the beginning of the 1990s new high-speed passenger lines in Spain have been built to the international standard gauge of 1,435 mm (4 ft 8+1⁄2 in), to allow these lines to link to the European high-speed network.
For example, in recent years Chile and Argentina have bought second hand Spanish/Portuguese Iberian-gauge rolling stock.
Due to the somewhat narrower gauge, a strong wear of the wheels may occur if the wheelset is not replaced.